JP3100148B2 - Sine wave approximation pulse width modulation signal generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sine wave approximate pulse width modulation signal generator, and more particularly to a sine wave that can be used for an inverter or the like that drives a compressor motor of an air conditioner. The present invention relates to a device for generating an approximate pulse width modulation (hereinafter simply referred to as “PWM”) signal.

[Prior art] As a conventional sine wave approximation PWM signal generator of this kind,
The technology described in Japanese Patent Application No. 63-31477 can be mentioned.

FIG. 7 shows a conventional sine wave approximation described in the above publication.
It is a block diagram showing a PWM signal generator.

In the figure, (1) is a CPU serving as a central processing unit of a microcomputer, (2) is a timer, (3) is a readable / writable RAM for storing waveform data, and (4) is a reference sine wave data. Read-only ROM,
(5) is an address pointer indicating a waveform generation data address in the waveform generation data table, and (6) is a port for generating a PWM signal. Note that two waveform generation data table areas are secured in the RAM (3). In the figure, the solid line indicates the flow of interrupt processing for generating a PWM signal, and the dotted line indicates the flow of main processing for generating waveform generation data.

Next, the operation of the sine-wave approximate PWM signal generator having the above configuration will be described with reference to the flowcharts of FIGS.

FIG. 8 shows P in the conventional sine wave approximate PWM signal generator.
FIG. 9 is a flowchart showing an interrupt processing operation of a WM signal, FIG. 9 is a flowchart showing a main processing operation in a conventional sine wave approximation PWM signal generator, and FIG. 10 is a data creation routine during the main processing operation of FIG. It is a flowchart.

First, the operation of generating a PWM signal will be described with reference to the flowchart of FIG. When a timer interrupt operation is started by an interrupt request by the timer (2), the address pointer (5) is incremented in step S1, and the RAM (3) is incremented in step S2.
It is determined whether or not the table is finished. This table is stored in RAM by the main processing described later.
(3) Created above. If the table is over, it is determined in step S3 whether or not the table needs to be switched. If the table needs to be switched (that is, if the output frequency or output power is to be changed), the process proceeds to step S3.
Switch the table with S4. Thereafter, the address pointer (5) is initialized in step S5. If the table does not end in step S2, the operations in steps S3 to S5 are not performed. Subsequently, in step S6, the contents of the table on the RAM (3) indicated by the address pointer (5) are set to C
The data is read by the PU (1), the port output data is output to the port (6), the time data is set in the timer (2) in step S7, and the interrupt processing ends. Thereafter, interrupt processing is started at a predetermined timing according to the time data in the waveform generation data, and a PWM signal is generated.

Next, the operation of creating waveform generation data on the RAM (3) will be described with reference to the flowcharts of FIGS. 9 and 10.

In FIG. 9, it is determined in step S11 whether there is a change in the frequency and voltage. If there is a change, the data creation program is called in step S12 and the data creation operation is executed. Return to But,
If there is no change in frequency and voltage in step S11, the data creation program is not called, and the process returns to the main routine. The data creation operation by the data creation program in step S12 is executed according to the procedure shown in FIG.

In FIG. 10, first, in step S21, the table not used by the timer interrupt is selected. next,
In step S22, 30-degree waveform generation data is created from the frequency data, the voltage data, the carrier frequency data, and the reference sine wave data in the ROM (4) by a triangular wave comparison method. Then, in step S23, this is expanded into data for 60 degrees, and in step S24, data that is short in time and cannot be processed by the microcomputer is cut.
When the creation of the data is completed, a flag indicating that the table can be switched is set in step S25, and thereafter, the process returns to the main routine again.

The timing at which such interrupt processing occurs and the PWM signal have a relationship as shown in FIG. FIG. 11 is a waveform diagram showing an interrupt processing generation timing in a conventional sine wave approximation PWM signal generator.

In FIG. 11, the arrows indicate the timing of the interrupt processing that occurs as described above. In this figure,
Four interrupts occur during one carrier cycle.

[Problem to be Solved by the Invention] In the conventional sine wave approximation PWM signal generator as described above, the carrier frequency is fixed as carrier frequency data (one-to-one correspondence with the output frequency), It was determined by the carrier frequency included in one rotation (360 degrees). In addition, the carrier frequency cannot be increased because interrupt processing is performed four times during one carrier cycle and there are many processes other than waveform data calculation, such as saving registers and the like.

In the conventional sine wave approximation PWM signal generator, RAM
(3) had two large waveform generation tables. However, usually, the capacity of RAM (3) is larger than the capacity of ROM (4).
Is not so large, so that when other programs coexist, it is greatly restricted and burdens the software.

On the other hand, as another prior art, there is a technique described in Japanese Patent Application Laid-Open No. 58-147231. This technique divides a clock pulse output from a clock pulse generator using a frequency division counter, and applies the obtained signal to a microprocessor as an interrupt pulse that gives the processing time of the microprocessor. Has been disclosed which synchronizes with a carrier signal. However, there is no disclosure about the timing of the output change of each phase when the interrupt processing is generated, and even if the time of the interrupt processing can be synchronized with the carrier signal, the carrier frequency must be automatically followed. Is something that cannot be done.

In addition, the technology described in Japanese Patent Application Laid-Open No. 62-213578 includes a technique for limiting the range of carrier data to be corrected when switching from an arbitrary phase synchronous PWM mode to a fixed phase synchronous PWM mode. PWM inverter device that can limit the current ripple during operation to a certain range, improve the reproducibility of output current, prevent the peak value of output current from increasing, and suppress the decrease in overload capability Is disclosed. That is, it has an arbitrary phase synchronous PWM mode. However, the technique of this publication discloses a technique of changing a carrier frequency by synchronizing an interrupt processing time with a carrier signal, but the carrier frequency is based on data in a carrier table, and the carrier frequency is arbitrarily determined. And the storage capacity of the waveform generation data table on the RAM cannot be reduced.

Accordingly, it is an object of the present invention to provide a sine-wave approximate PWM signal generator that can change a carrier frequency while eliminating the need for a waveform generation data table on a RAM.

[Means for Solving the Problems] A sine wave approximate PWM signal generating device according to the present invention includes a triangular wave carrier including a neighborhood including the highest point, a neighborhood including the lowest point, and a neighborhood including the highest point and the lowest point. Output change timing calculating means for calculating the timing of the output change of each phase when the interrupt processing is generated, according to the interrupt processing generated at any time; and the output change timing obtained by the calculation. Output change timing setting means for setting the output change timing each time the interrupt processing occurs, and storing the output change timing, and controlling the output of the PWM signal generated by the triangular wave comparison method according to the output change timing. Output control means, and carrier frequency changing means for reading and setting a predetermined parameter prepared in advance required for calculating the timing of the output change corresponding to the carrier frequency; It has.

[Operation] In the present invention, an interrupt process is generated at any point in the vicinity including the highest point of the triangular wave carrier, the vicinity including the lowest point, or the vicinity including the highest point and the lowest point,
By setting a carrier cycle in accordance with the occurrence of this interrupt processing, sequentially calculating the output change timing based on the carrier cycle, and setting the output change timing for each occurrence of the interrupt processing, Depending on the timing of the phase output change
It can output a PWM signal and change the carrier frequency.

[Example] Hereinafter, an example of the present invention will be described.

FIG. 1 is a block diagram showing a sine-wave approximate PWM signal generator according to an embodiment of the present invention.

In the figure, (11) is a CPU having functions as arithmetic means and timing setting means, (12) is a timer, (13)
Is a RAM for storing the voltage magnification, the carrier cycle data to be executed, the change amount of the address pointer for the carrier cycle, and the calculation result. (14) is reference sine wave data, standard output voltage data, and carrier cycle data corresponding to each carrier frequency. ROM (15) is an address pointer indicating an address for accessing reference sine wave data in the ROM (14), (16) is carrier cycle data, carrier magnification data, carrier in the ROM (14) An address pointer indicating an address for accessing a change amount of the address pointer for a cycle, (17) a port for outputting a PWM signal, and (18) a register for storing a PWM output change timing and an interrupt timing. Output control means for outputting to port (17) at timing or issuing an interrupt request to CPU (11), (19)
Is an I / O for inputting and outputting information to and from external devices and sensors.

Here, the above terms will be described. The “reference sine wave data” is a reference for generating sine wave data in a so-called triangular wave comparison method in which the sine wave data and the triangular wave carrier are compared to obtain ON / OFF timings (output change timings) of the switching elements of each phase. The “standard output voltage data” is data of an output voltage preset in a V / F pattern with respect to an output frequency, and the “voltage magnification” is an actual output voltage of the standard output voltage data. It is a coefficient when determining.

In this embodiment, the output voltage is changed based on the standard output voltage data by changing the voltage magnification in this manner.

FIG. 2 is a waveform diagram showing the generation timing of an interrupt process for calculating the output timing of a sine wave PWM waveform in the sine wave approximation PWM signal generator of FIG.

In the figure, (21) is a triangular wave carrier, and (22)
And (23) are part of the sine wave to be output. Arrows indicate the generation timing of the interrupt processing. In this figure, the interrupt occurs at both the vicinity including the uppermost point of the triangular wave carrier (21) and the vicinity including the lowermost point. Is shown.

Next, the operation of the sine-wave approximate PWM signal generator having the above configuration will be described. First, the overall flow of the interrupt processing operation will be described. FIG. 3 is a flowchart showing a PWM signal interrupt processing operation in the sine wave approximation PWM signal generator according to one embodiment of the present invention.

In FIG. 3, when an interrupt request is generated and the interrupt process is started, it is determined in step S31 whether the carrier is rising or falling. If the carrier is rising, the process of changing the carrier frequency is performed in step S32. Is performed. Subsequently, in step S33, the carrier cycle data set in step S32 is set in the timer (12). Thereafter, the interrupt processing is repeated at the set timer cycle. Then, every time the interruption process is performed, the process of calculating the output change timing is performed in step S34, and the calculation result is set in step S35.

Here, the operation of the main steps in FIG. 3 will be described with reference to the flowcharts in FIGS. 4 to 6.

FIG. 4 is a flowchart showing a processing routine of a carrier frequency changing operation executed in step S32 of FIG. 3, and this operation is performed by a carrier frequency changing means.

In FIG. 4, first, in step S41, it is determined whether or not the address pointer of the carrier frequency for changing the carrier frequency is set by the external or internal processing of the microcomputer. In step S42, carrier cycle data is read in accordance with the address pointer (16), and this data is stored in the RAM (13) in step S43. Then, step S4
In step 4, the carrier magnification data is read in accordance with the address pointer (16), and this data is stored in the RAM in step S45.
(13) Remember on top. Similarly, in step S45, the change amount of the address pointer (16) for the carrier cycle is read out according to the address pointer (16), and in step S47, the RAM is read.
(13) Remember on top. On the other hand, when the carrier frequency is not changed in step S41, the operations from step S42 to step S57 are not performed. By such a series of operations, the process of changing the carrier frequency is performed.

FIG. 5 is a flowchart showing a processing routine of a calculation operation executed in step S34 of FIG. 3, and this operation is performed by output change timing calculation means.

In FIG. 5, first, in step S51, predetermined reference sine wave data is read from the address indicated by the address pointer (15). In step S52, the reference sine wave data read in step S51 is multiplied by the carrier cycle magnification data, and reference sine wave data corresponding to the carrier frequency to be executed is calculated. In step S53, the ROM
The standard output voltage data stored in (14) and transferred to the RAM (13) by the main processing is multiplied by the voltage magnification data stored in the RAM (13). The timing of the output change during the rising of the carrier is calculated, and the calculation result is stored in the RAM (13) in step S54. Next, in order to calculate the output change timing during the carrier descending, in step S55, the output change timing data obtained in step S33 is subtracted from the carrier cycle data in the RAM (13). Is stored in the RAM (13) in step S56. Next, in order to calculate the output change timing of the other phase, the address pointer (15) is advanced by a value corresponding to the phase difference in step S57, and the reference sine is calculated from the address indicated by the address pointer (15) in step S58. The wave data is read, multiplied by the carrier cycle magnification data in step S59, and reference sine wave data corresponding to the carrier to be executed is calculated. Then, in step S60, the reference sine wave data, the standard output data, and the voltage magnification data are multiplied, and the multiplication result is stored in step S61. Subsequently, in order to calculate the timing of the output change during the lowering of the carrier, in step S62, the result obtained in step S60 is subtracted from the carrier cycle data in the RAM (13).
The result is stored in step S63. Next, step S
In 64, the change amount of the address pointer for the carrier cycle is RAM
The address read from (13) is added to the address pointer (15). If the address exceeds the range of the sine wave data table in step S65, the address pointer is initialized in step S66. By such a series of operations, the arithmetic processing of the output change timing is performed.

FIG. 6 is a flowchart showing a processing routine of a timing setting operation executed in step S35 of FIG. 3, and this operation is performed by output change timing setting means.

In FIG. 6, first, in step S71, it is determined whether to set the timing when the carrier is rising or the timing when the carrier is falling. If the timing when the carrier is rising is set, the process proceeds to step S72. The output change timing stored in step S54 in FIG. 5 is set in the output control means (18). In step S73, the output change timing stored in step S61 in FIG. ) Is set. On the other hand, when setting the timing when the carrier is descending, step S74
Then, the output change timing stored in step S56 in FIG. 5 is set in the output control means (18), and in step S75, the output change timing stored in step S63 in FIG. Set to (18).
Through such a series of operations, the output change timing is set.

As described above, the sine-wave approximation PWM signal generating apparatus of this embodiment includes the vicinity including the highest point of the triangular wave carrier, the vicinity including the lowest point, and the vicinity including the highest point and the lowest point of the triangular wave carrier performed during the main processing. The output change timing as shown in the flowchart of FIG. 5 for calculating the timing of the output change of each phase when the interrupt processing occurs according to the interrupt processing occurring at any one of the following points: An arithmetic means, an output change timing setting means for setting the timing of the output change obtained by the calculation each time the interrupt processing occurs, and an output change timing setting means as shown in the flowchart of FIG. Output control means (18) for storing and controlling the output of the PWM signal generated by the triangular wave comparison method in accordance with the timing of the output change; The fourth to read setting predetermined parameters because prepared corresponding to the carrier frequency
And a carrier frequency changing unit as shown in the flowchart of FIG.

Then, an interrupt process occurs at any point in the vicinity including the highest point of the triangular wave carrier, the vicinity including the lowest point, or the vicinity including the highest point and the lowest point. By setting the carrier cycle and calculating the output change timing sequentially based on the carrier cycle, and setting the output change timing each time an interrupt process occurs, the output change timing of each phase can be set. Output a PWM signal.

Therefore, in this embodiment, the carrier frequency is not fixed as carrier frequency data as in the related art, but the carrier frequency can be changed. Also,
It is not necessary to have two large waveform generation tables in the RAM as in the conventional case, and there is no interruption processing performed four times during one carrier period as in the conventional case. Since the number of interrupt processes that occur is reduced, even when other programs coexist, there is no major restriction.
As a result, the burden on the software can be reduced.

The output change timing calculating means, output change timing setting means, output control means, and carrier frequency changing means of the above embodiment may be all constituted by hardware and software of a one-chip microcomputer. May be configured as an external mechanism.

[Effects of the Invention] As described above, the sine-wave approximation PWM signal generation device of the present invention includes an output change timing calculation unit that calculates the output change timing of each phase when an interrupt process occurs, Output change timing setting means for setting the timing of each time the interrupt processing occurs, output control means for controlling the output of a PWM signal generated by a triangular wave comparison method according to the timing of the output change, and Carrier frequency changing means for reading and setting the parameters of the triangular wave carrier in accordance with the carrier frequency, the vicinity including the highest point, the vicinity including the lowest point, or the vicinity including the highest point and the lowest point. An interrupt process occurs at any time, a carrier cycle is set in accordance with the occurrence of the interrupt process, and the output change timing is sequentially determined based on the carrier cycle. , And by setting the output change timing for each occurrence of interrupt processing, a PWM signal can be output according to the output change timing of each phase, so that the carrier frequency can be changed, In addition, the number of interrupts that occur in one carrier cycle is reduced, and the waveform generation data table on the RAM is not required. Therefore, even when other programs coexist, there is no major restriction, and the software load is reduced. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a sine wave approximation PWM signal generator according to an embodiment of the present invention. FIG. 2 is a waveform diagram showing interrupt processing generation timing in the sine wave approximation PWM signal generator of FIG. FIG. 3 is a flowchart showing an interrupt processing operation in the sine wave approximation PWM signal generator according to one embodiment of the present invention, and FIG. 4 shows a processing routine of a carrier frequency changing operation during the interrupt processing operation of FIG. 5 is a flowchart showing a processing routine of an arithmetic operation during the interrupt processing operation of FIG. 3, and FIG. 6 is a flowchart showing a processing routine of a timing setting operation during the interrupt processing operation of FIG. FIG. 7 is a block diagram showing a conventional sine wave approximation PWM signal generator, and FIG. 8 is a flowchart showing a PWM signal interruption processing operation in the conventional sine wave approximation PWM signal generator. Figure conventional sine wave approximation
FIG. 10 is a flowchart showing a main processing operation in the PWM signal generator, FIG. 10 is a flowchart showing a data creation routine during the main processing operation of FIG. 9, and FIG. 11 is an interrupt processing generation in the conventional sine wave approximation PWM signal generator. FIG. 4 is a waveform chart showing timing. In the figure, 11: CPU, 12: timer 13: RAM, 14: ROM 15, 16: address pointer 17: port, 18: output control means 19: I / O. In the drawings, the same reference numerals and symbols indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. An interrupt processing which is generated at a predetermined time of a triangular wave carrier of any one of a neighborhood including the highest point of the triangular wave carrier, a neighborhood including the lowest point, and a neighborhood including the highest point and the lowest point. An output change timing calculating means for calculating an output change timing of each phase when the interrupt processing is generated; and the interrupt processing generates the output change timing obtained by the calculation of the output change timing calculating means. Output change timing setting means, which is set each time the operation is performed, storing the output change timing obtained by the calculation of the output change timing calculating means, and a pulse width generated by a triangular wave comparison method according to the output change timing Output control means for controlling the output of the modulation signal; and the output change timing calculating means prepared in advance for calculating the output change timing. Sine wave approximation PWM signal generating apparatus characterized by comprising a carrier frequency changing means for reading setting predetermined parameters corresponding to the carrier frequency.